Recommend you read the first post in this thread.
IpCamera: New IP Camera Binding - Add-ons / Bindings - openHAB Community
If you want the cheapest, that would be a esp32 camera, however I do not see these as good value as you get bad quality picture, no night vision and missing features like motion detection done on board. In some cases like a camera in your dogs kennel, you may be happy with this.